At the end of the NPB season, the top teams in each league face off in the Japan Series. Prior to 2005, the only other interleague confrontation came in the form of two All-Star Games played about two-thirds of the way through the season. In 2005, NPB began to incorporate interleague play.

Major differences between NPB and MLB include the much smaller farm system in Japan (only one minor league team per franchise), shorter seasons (usually ranging between 130 and under 150 games), multiple All-Star Games per year and less player mobility. There are far fewer trades in Japan than in the majors and free agency starts later in a player's career.